This invention relates generally to a coronary sinus catheter, and more particularly to a balloon catheter useful in the retrograde administration of cardioplegia through the coronary sinus.
Cardioplegia is a commonly used technique for protecting the heart during heart surgery. Typically, cooled cardioplegia solution (e.g., a potassium solution) is administered to the patient's heart in the antegrade direction through the patient's aorta. "Antegrade" refers to the direction of normal blood flow, and "retrograde" refers to the direction opposite of normal blood flow. The cardioplegia solution stops the heart and reduces its temperature to minimize damage to the heart during surgery.
In recent years, there has been increasing interest in administering cardioplegia in the retrograde direction (opposite of normal blood flow) via the coronary sinus. Such retrograde cardioplegia has been used with patients having critical coronary artery stenosis making diffusion of cardioplegia in the antegrade direction difficult and inefficient, and with patients suffering aortic valve disease. P. Menasche et al., "Retrograde Coronary Sinus Perfusion: A Safe Alternative for Ensuring Cardioplegic Delivery in Aortic Valve Surgery", The Annals of Thoracic Surgery, Vol. 34, No. 6, pages 647-658 (December 1982). See, also, J. Solorzano et al., "Retrograde Coronary Sinus Perfusion for Myocardial Protection during Cardiopulmonary Bypass", The Annals of Thoracic Surgery, Vol. 25, No. 3, pages 201-208 (March 1978); and D. Lolley et al., "Myocardial Distribution of Asanguineous Solutions Retroperfused under Low Pressure through the Coronary Sinus", J. Cardiovascular Surg., 21:287-294 (1980).
One difficulty in administering cardioplegia via the coronary sinus is that the sinus walls are slippery, extensible and are tapered such that the sinus vessels become smaller in the direction in which a catheter is advanced into the sinus vessel. See, e.g., U.S. Pat. No. 4,927,412, at column 1, lines 7-23. Techniques that have been developed to help secure balloon catheters in the coronary sinus include having someone manually hold the catheter in position during the surgery, or tying the catheter in position with a purse-string suture.
Dislodgement of such balloon catheters has been a longstanding issue with cardiovascular surgeons, which has even limited acceptance of the retrograde procedure. Acceptance of one fairly new technique, the continuous administration of "warm" cardioplegia, has been limited due to concerns regarding the ability of currently available catheters to stay in place in the coronary sinus. Dislodgement of the catheter during administration of warm cardioplegia may go undetected with potentially serious consequences.
U.S. Pat. No. 4,927,412 (Menasche) discloses a coronary sinus catheter for use in administering cardioplegia solution in the retrograde direction via the coronary sinus. That catheter includes an elongate member, and a balloon mounted on the elongate member. The elongate member has at least two lumens including one lumen in fluid communication with the interior of the balloon. The balloon includes at least one truncated conical surface having outwardly-facing spaced-apart parallel concentric lands formed thereon for frictionally engaging the coronary sinus. That catheter does not include a pressure sensor on the balloon inflation line.
The balloon described in U.S. Pat. No. 4,927,412 (Menasche) is formed of silicone rubber having a hardness of approximately 50 on the Shore A scale. The lands of that balloon are generally hemispherical in cross section having a radius of approximately 0.015 inches (0.038 millimeters), and are spaced apart a distance of approximately 0.05 inches (1.27 millimeters). The wall thickness of that balloon is approximately 0.030 inches (0.762 millimeters).
The balloon described in U.S. Pat. No. 4,927,412 (Menasche) was particularly designed for use with an open atrium technique. In the "open atrium" technique, the right atrium of the heart is substantially opened up with a large incision (e.g., two inches (50 mm)) so that direct access is provided to the coronary sinus. The distal end of the retrograde catheter is then inserted directly into the coronary sinus and the balloon is inflated to engage the walls of the coronary sinus.
While there are some advantages to the open atrium technique, one disadvantage is the inability to use a "Two-stage" venous catheter to drain the inferior vena cava and the right atrium. "Two-stage" venous catheters are sold under the trade designation "SARNS Two-Stage Venous Return Catheter" by Minnesota Mining and Manufacturing Company, St. Paul, Minn. Such "Two-stage" catheters are inserted through a small incision into the right atrium until the smaller diameter distal end portion of the catheter is positioned in the inferior vena cava. The smaller diameter, distal portion of the "Two-stage" catheter drains venous blood from the inferior vena cava, and the larger diameter portion, which is immediately proximal the distal portion, drains blood from the right atrium. The drained blood is then supplied to the extracorporeal support circuit, where among other things it is oxygenated before being returned to the patient. In the "open atrium" technique, two catheters (in addition to the retrograde catheter) must be used to perform the same function as the "Two-stage" venous catheter.
Many surgeons prefer to use a "blind" procedure as opposed to the "open atrium" technique. Only a small incision is made to gain access to the right atrium and the coronary sinus with the "blind" technique. Advantages of the "blind" procedure include making a smaller incision and allowing the use of the "Two-stage" venous catheter. The balloon thickness and durometer specified in U.S. Pat. No. 4,927,412 result in a balloon that is stiff enough to be difficult to use in the blind technique.
DLP, Inc., Grand Rapids, Mich., and RMI, Inc., Salt Lake City, Utah, sell retrograde catheters under the trade designations "dlp Retrograde Coronary sinus Perfusion Cannula (Model Code No. 94015 (15 French))" and "RETROPLEGIA Coronary Sinus Perfusion Cannula (Catalog Nos. RCS-014, RC-014-MIB and RC-014-MIBB)", respectively.
The "DLP" cannula comprises a wire-wound silicone rubber cannula body with a beveled tip. The DLP cannula includes an inflatable retention balloon mounted on the cannula body approximately 3/8 inches (10 mm) from the beveled tip, and an inflation assembly at the proximal end of the cannula for inflating the retention balloon. When not inflated, the "DLP" balloon has a very low profile and conforms fairly closely with the surface of the cannula body.
The DLP inflation assembly consists of an expandable balloon in fluid communication with the inflatable retention balloon, and a one-way valve between the expandable balloon and a luer fitting adapted to receive a fluid syringe for inflating the retention balloon. The arrangement is such that the expandable balloon, which is visible in use, is expanded when the inflatable retention balloon, which is inside the coronary sinus in use, is inflated. This provides an indication of pressure in the retention balloon. The visible/expandable "DLP" balloon has a wall thickness of approximately 0.019 inches (0.48 mm).
The "DLP" inflatable retention balloon, after being cut open, was measured to have a wall thickness of 0.019 inches (0.48 millimeters) when not inflated. From this figure, the inflated "DLP" retention balloon was calculated to have a wall thickness of approximately 0.006 inches (0.15 millimeters) when inflated.
RMI sells at least three retrograde cannulae including (1) a 14 French cannula with a "self-inflating/deflating" retention balloon and an insertion stylet (Catalog No. RCS-014); (2) a 14 French cannula with a manually inflatable balloon and a malleable stylet (Catalog No. RC-014-MIB); and (3) a 14 French cannula with a manually inflatable balloon and a "Buckberg" stylet (Catalog No. RC-014-MIBB).
The manually inflatable balloon of the "RMI" catheter sold under Catalog No. RC-014-MIB, after being cut open, was measured to have a wall thickness of 0.017-0.019 inches (0.43-0.48 millimeters) when not inflated. From this figure, the inflated "RMI" balloon was calculated to have a wall thickness of approximately 0.006 inches (0.15 millimeters) when inflated. Like the "DLP" balloon, that "RMI" balloon (Catalog No. RC-014-MIB) conforms fairly closely with the surface of the cannula when the balloon is not inflated.
One problem with both the "DLP" and "RMI" cannulae models with uninflated balloons that conform to the surface of the cannula is that the balloons when inflated tend to become displaced relative to the longitudinal axis of the cannula. This allows the distal end of the catheter to become displaced toward the walls of the coronary sinus.
U.S. Pat. No. 5,021,045, which may relate to RMI's "self-inflating/deflating" cannula sold under catalog No. RCS-014, describes a retrograde cannula having a retention balloon which is filled with the infusion fluid via openings between the infusion lumen and the interior of the balloon. That balloon is "constructed so that it is not necessary for the balloon to expand significantly from its unfilled state in order to seal the coronary sinus." See, e.g., column 9, lines 3-9, of U.S. Pat. No. 5,021,045. As reported in U.S. Pat. No. 5,021,045, that balloon is formed of polyurethane, and has a wall thickness within the range of 0.003-0.005 (0.004) inches (0.076-0.127 mm (0.102 mm)).
U.S. Pat. No. 5,021,045 also describes a particular ratio of cross-sectional areas between the infusion lumen outlets and the openings between the balloon and the infusion lumen, which among other things is apparently necessary in order for the balloon to be self-filling. While U.S. Pat. No. 5,021,045 discusses avoidance of "jet-like flow" exiting the catheter by regulating the above ratio and boring the infusion lumens at an angle, it has been found that the RMI cannulae sold under Catalog Nos. RCS-014 and RC-014-MIB spray a thin stream of fluid through each outlet for a distance of several inches when saline solution is delivered through the infusion lumen and the cannula is held in air.